Letoff for looms



April 23, 1946, c DARWIN 2,398,925

LET-OFF FOR LOOMS Filed April 5, 1945 2 Sheets-Sheet 1 INvsN-roR:

(luv-Tom) DARw 1 N zwf/f M10 NEY April 23, 1946. c DARWIN 2,398,925

LET-OFF FOR LOOMS Filed April 5, 1945 2 Sheets-Sheet 2 INVENTOR:

O CLIFFORD DARWIN aw. V-

ATTORNEY Patented Apr. 23, 1946 LETOFF FOR LOOMS Cllflol'fl' Darwin,Worcester, Mass, assignor to Crompton & Knowles Loom Works, Worcester,Mass., a corporation of Massachusetts Application April 5, 1945, SerialNo. 586,758

3 Claims.

This invention relates to improvements in letoff mechanisms for loomsand it is the general biect of the invention to provide a dampener forthe escapement mechanism of the letoff.

' A type of letofl which has gone into extensive use employs anescapement wheel connected by./

gearing to the warp beam. The wheel cooperates with an escapement levercontrolled by a brake the position of which is determined by mechanismintermediate the whip roll and the brake. Under normal conditions thebrake holds the escapement lever against oscillation andthereforeprevents turning of the escapement wheel with the result that the warpbeam is held against rotation. The warp passes over a whip roll whichmoves forwardly during the time that the warp beam is locked againstrotation, and when the whip r011 reaches a given forward position itacts through intermediate mechanism to move the brake to non-brakingposition, whereupon the escapement lever is free to rock by a forceoriginating in the warp and transmitted through the escapement wheel.

When light-weight goods are being woven a letoff of this type operatessatisfactorily, the brake being alternately on and off during loomoperation and the escapement wheel-turning intermittently and uniformly.When heavy-weight goods are being woven, however, the tension set up inthe warp is so high that when the brake is released the escapement wheelhas a tendency to spin or rotate at such a fast rate that warp is letoff fasterthan it can be properly tensioned by rearward movement of thewhip roll. The purpose of the escapement lever is to prevent too rapid aturning of the escapement wheel, but the lever does not perform thisfunction under-all conditions, and the net result of its failure'tooperate correctly when heavy cloth is being woven. is to produce anobjectionable slackness in the warp which results in imperfections inthe cloth.

It is an important object of my present invention to provide a dampenerwhich will prevent too rapid an oscillation of the escapement lever andthereby'reduce the speed at which the escape-- ment wheel turns when itis subjected toco'nsiderable rotary force whenever the brake is releasedduring the weaving of heavy fabrics.

The escapement wheel shows a tendencyto spin which increasesprogressively as the weight of goods being woven is increased. Thus, amedium weight goods will cause a small amount of spinv nism to'theweaving of a variety of weights of fabric it is another object of myinvention to provide means for imposing a variable dampening force onmovement of the escapement lever so that the rate at which it canoscillate will be regulated more or less in proportion to the weight ofthe fabric being woven.

With these and other objects in view which will appear as thedescription proceeds, my, in-

vention resides in the combination and arrangement of parts hereinafterdescribed and set forth.

In the accompanying drawings, wherein two forms of the invention ar setforth,

Fig. 1 is a side elevation of a loom letofl mechanism having myinvention appliedthereto,

Fig. 2 is a rear elevation of the mechanism shown looking in thedirection of arrow 2, Fig. 1, Fig. 3 is a horizontal section on line 3-4of Fig.

1 and Fig. 4 is a view similar to a portion of Fig. -1 but showing amodified form of the invention.

Referring particularly to Figs. 1 and 2, -I have shown a loom frame Hito which is secured a rearwarly extending upper support ii having a.pivot it around which swings an upright lever 18. A whip roll it isjournaled as at it in the upper end of lever l3 and moves backwardly andforwardly in response to variations in tension existing in the warp W.Stops i8 and ii on the lever 3 and support, respectively, limit rearwardmove ment of the whip roll. I

A weight lever 20 is pivoted as at 2| to the support H and has means forsupporting a weight 22 at difierent distances from the pivot M. A

v link 23 connects the upper part of weight lever 20 with a whip rolllever 24 pivoted on'suppo t ii and having an arm 25 which bears againstthe front of upright lever 'i3. Under normal conditions the weight 22tends to mov'e'link 23 to the right as viewed in Fig. 2 and cause arm 25to I As the whi roll moves forwardly lever it rocks lever and the latteracts through link 23 to turn exert a rearward force on the whip roll.

lever 20 in a counter' clockwise direction as viewed .45 in Fig. 2 toraise weight 22. i Y 11 A rod 28 is connected to lever 20 and extendsdownwardlyior connection with a. brake lever 2'l'pivoted as at 28 -to asecond support 28 extending rearwardly from the loomside. The rear endof lever-21 carries a brake shoe 30 which en- ""gages. a web at on anescapement lever 32 pive oted as at 33 to the lower support 29.Escapement fingers 34 and 35 on lever 82 cooperate with an escapementwheel Sii'turning on a stud 31 supported by the part 29. Intermediateconnections not illustrated herein are interposed between the escapementwheel and the warp beam B so that these two parts turn together, theescapement wheel however having a much more rapid angular movement thandoes the warp beam.

Under normal weaving conditions it may be assumed that weight 22 will bedown so that the rear end of lever 21 is up to hold the brake shoe 3!!against the web 3| of the escapement lever. Under these conditions thefingers 34 and 33 are held stationary and prevent turning of theescapement wheel. As weaving continues the whip roll advances and indoing so causes lever 20 to rise and eflect lowering of the rear end oi!lever 21 to move the brake shoe away from its web, whereupon theescapement lever is tree to rock. The tension of the warp. istransmitted mm the beam to the escapement wheel and tends to turn thelatter so that the warp beam may turn in a clockwise direction as viewedin Fig. 1 to unwind warp. As the warp unwinds weight 22 acts throughlever 24 to move the whip roll rearwardly or to the left as viewed inFig. 1 and eventually the brake shoe will engage: the web 3i and arrestfurther turning of the escapement wheel and beam. This operation goes onduring weaving, the escapement wheel being alternately locked andunlocked and when unlocked being responsive to forces derived from thewarp tending to turn it. If the warp is heavy and exerts considerabletension the escapement lever as heretofore made will not be able toimpose sufficient restraint on the escapement wheel to prevent it fromturning very rapidly or spinning on its axis. 1

The matter thus far described of itself forms no part of my presentinvention and may be made as set forth in prior patent to Payne2,184,059 to which reference maybe had for parts of the letof!mechanismnot specifically described herein, such as the connectionsbetween the escapement wheel and warp beam.

In carrying my present invention into effect I provide the escapementlever with a dampener which has the effect of preventing the lever fromoscillating too rapidly when the brake shoe is released and theescapement wheel is subject to a strong force tending to turn it. Thepreferred form of the invention shown in Figs. 1, 2 and 3 comprises aweight 40 having a rearwardly extending arm 4| pivoted as at 42 to arearward extension 43 of the escapement lever 32. The latter is providedwith an arcuate slot 44, see Fig. 1, concentric with the axis 42 andreceiving a bolt 45 which passes through the arm 4i. This bolt has ahead 46 and a nut 41 as shown in Fig. 3 by means of which the weight canbe held fixed in angularly adjusted position with respect to theescapement lever 32. Thus, when weight 40 is in its lowest position asshown in full lines in Fig. 1, bolt 45 will be at the bottom of slot 44and the center of gravity of the lever 32 will be low and at aconsiderable distance from the stud or axis 33 around which the lever 32rocks. When the weight 40 is in the high position, shown in dotted linesin Fig. l. the center oi gravity of the escapement lever is relativelyhigh and near the axis 33. When the weight is low its inertia imposes aconsiderable dampening action on the oscillation oi lever 32 which tendsto prevent spinning of the escapement wheel. This is the setting-whichthe weight has when the loom is weaving heavy fabric. when the weight isin its high position the moment of inertia of the lever 32 is less andthe fingers 34 and 35 exert less restraint on the turning of theescapement wheel.

This condition exists when the fabric being woven is of medium grade.This last setting of the weight may also be used when the fabric beingwoven is light, or the weight may be entirely removed.

In the modified form of the invention shown in Fig. 4 a weight 50 issecured as at 51 to the lower end or a depending link 52 which issecured as at 53 to the escapement lever 32. Weight 50 may be used whena heavy iabric is being woven and removed when a light fabric is beingwoven.

From the foregoing it will be seen that I have provided dampening meansfor the escapement mechanism of a letoil mechanism so constructed thatthe moment of inertia of the escapement lever may be varied dependingupon the weight of the fabric being woven in the loom. This variation isattained by. changing the position of weight 40 with respect to the axis33 of the escapement lever. When in different positions due to theadjustment afforded by the slot 44 and bolt 45 the weight can imposevarying degrees of inertia on the escapement lever to adapt the let-offto the weaving of a wide range of fabrics. In the modified form of theinvention the weight 50 is maintained at a fixed distance from the axis33 and can be used when heavy fabrics are being woven and removed whenlight fabrics are being woven.

Having thus described my invention it will be seen that changes andmodifications may be made therein by those skilled in the art withoutdeparting from the spirit and scope of the invention and I do not wishto be limited to the details herein disclosed, but what I claim is:

1. In a letoff for a loom capable of weaving with a variety of warps inwhich various degrees of warp tension exist, the loom having a warp beamand an escapement wheel turning therewith and having a whip roll movablein response to changes in warp tension and controlling a brake, theescapement wheel tending to turn faster when the warp'tension is highthan when said tension is low, an escapement lever controlled by thebrake and cperatively related to the escapement wheel to regulate therate of turning thereof, a pivot for said lever, a weight for saidlever, and means to secure said weight to said lever at difierentdistances from said pivot, whereby the moment of inertia of said levermay be varied.

2. In a letofl for a loom capable of weaving with a variety of warps inwhich various degrees of warp tension exist, the loom having a warp beamand an escapement wheel turning therewith and having a whip roll movablein response to changes in warp tension and controlling a brake, theescapement wheel tending to' turn faster when the warp tension is highthan when said tension is low, an escapement lever controlled by thebrake and operatively related to the escapement wheel to regulate therate oi turning thereof, a pivot for said lever, a weight pivotallymounted on said lever for movement toward and from the pivot of thelever, and means to hold said weight fixed to said lever at any one of aplurality of distances from the pivot of the lever to vary the moment ofinertia of said lever.

3. In a letofl. for aloom capable of weaving with a variety of warps inwhich various degrees of warp tension exist. the loom having a warp beamand an escapement wheel turning therewith and having a whip roll movablein response to changes in warp tension and controlling a brake, theescapement wheel tending to turn faster when the warp tension is highthan when said tension is low, an escapement lever controlled by thebrake and operatively related to the escapement wheel to regulate therate of turning thereof, a pivot for said lever, a weight pivotallymounted on said lever for movement toward and from the pivot of thelever, a slot in said lever concentric with the axis of said weight, andmeans passing through said slot to hold the weight fixed to the lever inany one of a plurality of distances from the pivot of the lever to varythe moment of inertia of said lever.

CLIFFORD DARWIN.

